Prior an comparators used in A/D converters are usually either a linear mode differential circuit or an offset cancelling circuit involving switches and capacitors. The linear mode differential comparators can be designed with either bipolar or MOS devices although high speed operation usually requires bipolar devices in the signal path. The offset cancelling circuits are usually CMOS circuits that use switches and capacitors to remove the effects of the relatively large offset voltages common with small MOS devices. Regardless of the circuit topology or design, all comparators intended for use in A/D converters must meet constraints on power dissipation, circuit complexity and layout area, voltage resolution, and operating speed.